/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
* 
*      http://www.apache.org/licenses/LICENSE-2.0
* 
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.xinqihd.sns.gameserver.util;

import java.util.Random;
/**
* <p>Operations for random <code>String</code>s.</p>
* <p>Currently <em>private high surrogate</em> characters are ignored. 
* These are unicode characters that fall between the values 56192 (db80)
* and 56319 (dbff) as we don't know how to handle them. 
* High and low surrogates are correctly dealt with - that is if a 
* high surrogate is randomly chosen, 55296 (d800) to 56191 (db7f) 
* then it is followed by a low surrogate. If a low surrogate is chosen, 
* 56320 (dc00) to 57343 (dfff) then it is placed after a randomly 
* chosen high surrogate. </p>
*
* @author Apache Software Foundation
* @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
* @author Gary Gregory
* @author Phil Steitz
* @since 1.0
* @version $Id: RandomStringUtils.java 905636 2010-02-02 14:03:32Z niallp $
*/
public class RandomStringUtils {

   /**
    * <p>Random object used by random method. This has to be not local
    * to the random method so as to not return the same value in the 
    * same millisecond.</p>
    */
   private static final Random RANDOM = new Random();

   /**
    * <p><code>RandomStringUtils</code> instances should NOT be constructed in
    * standard programming. Instead, the class should be used as
    * <code>RandomStringUtils.random(5);</code>.</p>
    *
    * <p>This constructor is public to permit tools that require a JavaBean instance
    * to operate.</p>
    */
   public RandomStringUtils() {
     super();
   }

   // Random
   //-----------------------------------------------------------------------
   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of all characters.</p>
    *
    * @param count  the length of random string to create
    * @return the random string
    */
   public static String random(int count) {
       return random(count, false, false);
   }

   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of characters whose
    * ASCII value is between <code>32</code> and <code>126</code> (inclusive).</p>
    *
    * @param count  the length of random string to create
    * @return the random string
    */
   public static String randomAscii(int count) {
       return random(count, 32, 127, false, false);
   }
   
   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of alphabetic
    * characters.</p>
    *
    * @param count  the length of random string to create
    * @return the random string
    */
   public static String randomAlphabetic(int count) {
       return random(count, true, false);
   }
   
   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of alpha-numeric
    * characters.</p>
    *
    * @param count  the length of random string to create
    * @return the random string
    */
   public static String randomAlphanumeric(int count) {
       return random(count, true, true);
   }
   
   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of numeric
    * characters.</p>
    *
    * @param count  the length of random string to create
    * @return the random string
    */
   public static String randomNumeric(int count) {
       return random(count, false, true);
   }

   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of alpha-numeric
    * characters as indicated by the arguments.</p>
    *
    * @param count  the length of random string to create
    * @param letters  if <code>true</code>, generated string will include
    *  alphabetic characters
    * @param numbers  if <code>true</code>, generated string will include
    *  numeric characters
    * @return the random string
    */
   public static String random(int count, boolean letters, boolean numbers) {
       return random(count, 0, 0, letters, numbers);
   }
   
   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of alpha-numeric
    * characters as indicated by the arguments.</p>
    *
    * @param count  the length of random string to create
    * @param start  the position in set of chars to start at
    * @param end  the position in set of chars to end before
    * @param letters  if <code>true</code>, generated string will include
    *  alphabetic characters
    * @param numbers  if <code>true</code>, generated string will include
    *  numeric characters
    * @return the random string
    */
   public static String random(int count, int start, int end, boolean letters, boolean numbers) {
       return random(count, start, end, letters, numbers, null, RANDOM);
   }

   /**
    * <p>Creates a random string based on a variety of options, using
    * default source of randomness.</p>
    *
    * <p>This method has exactly the same semantics as
    * {@link #random(int,int,int,boolean,boolean,char[],Random)}, but
    * instead of using an externally supplied source of randomness, it uses
    * the internal static {@link Random} instance.</p>
    *
    * @param count  the length of random string to create
    * @param start  the position in set of chars to start at
    * @param end  the position in set of chars to end before
    * @param letters  only allow letters?
    * @param numbers  only allow numbers?
    * @param chars  the set of chars to choose randoms from.
    *  If <code>null</code>, then it will use the set of all chars.
    * @return the random string
    * @throws ArrayIndexOutOfBoundsException if there are not
    *  <code>(end - start) + 1</code> characters in the set array.
    */
   public static String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars) {
       return random(count, start, end, letters, numbers, chars, RANDOM);
   }

   /**
    * <p>Creates a random string based on a variety of options, using
    * supplied source of randomness.</p>
    *
    * <p>If start and end are both <code>0</code>, start and end are set
    * to <code>' '</code> and <code>'z'</code>, the ASCII printable
    * characters, will be used, unless letters and numbers are both
    * <code>false</code>, in which case, start and end are set to
    * <code>0</code> and <code>Integer.MAX_VALUE</code>.
    *
    * <p>If set is not <code>null</code>, characters between start and
    * end are chosen.</p>
    *
    * <p>This method accepts a user-supplied {@link Random}
    * instance to use as a source of randomness. By seeding a single 
    * {@link Random} instance with a fixed seed and using it for each call,
    * the same random sequence of strings can be generated repeatedly
    * and predictably.</p>
    *
    * @param count  the length of random string to create
    * @param start  the position in set of chars to start at
    * @param end  the position in set of chars to end before
    * @param letters  only allow letters?
    * @param numbers  only allow numbers?
    * @param chars  the set of chars to choose randoms from.
    *  If <code>null</code>, then it will use the set of all chars.
    * @param random  a source of randomness.
    * @return the random string
    * @throws ArrayIndexOutOfBoundsException if there are not
    *  <code>(end - start) + 1</code> characters in the set array.
    * @throws IllegalArgumentException if <code>count</code> &lt; 0.
    * @since 2.0
    */
   public static String random(int count, int start, int end, boolean letters, boolean numbers,
                               char[] chars, Random random) {
       if (count == 0) {
           return "";
       } else if (count < 0) {
           throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
       }
       if ((start == 0) && (end == 0)) {
           end = 'z' + 1;
           start = ' ';
           if (!letters && !numbers) {
               start = 0;
               end = Integer.MAX_VALUE;
           }
       }

       char[] buffer = new char[count];
       int gap = end - start;

       while (count-- != 0) {
           char ch;
           if (chars == null) {
               ch = (char) (random.nextInt(gap) + start);
           } else {
               ch = chars[random.nextInt(gap) + start];
           }
           if ((letters && Character.isLetter(ch))
               || (numbers && Character.isDigit(ch))
               || (!letters && !numbers)) 
           {
               if(ch >= 56320 && ch <= 57343) {
                   if(count == 0) {
                       count++;
                   } else {
                       // low surrogate, insert high surrogate after putting it in
                       buffer[count] = ch;
                       count--;
                       buffer[count] = (char) (55296 + random.nextInt(128));
                   }
               } else if(ch >= 55296 && ch <= 56191) {
                   if(count == 0) {
                       count++;
                   } else {
                       // high surrogate, insert low surrogate before putting it in
                       buffer[count] = (char) (56320 + random.nextInt(128));
                       count--;
                       buffer[count] = ch;
                   }
               } else if(ch >= 56192 && ch <= 56319) {
                   // private high surrogate, no effing clue, so skip it
                   count++;
               } else {
                   buffer[count] = ch;
               }
           } else {
               count++;
           }
       }
       return new String(buffer);
   }

   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of characters
    * specified.</p>
    *
    * @param count  the length of random string to create
    * @param chars  the String containing the set of characters to use,
    *  may be null
    * @return the random string
    * @throws IllegalArgumentException if <code>count</code> &lt; 0.
    */
   public static String random(int count, String chars) {
       if (chars == null) {
           return random(count, 0, 0, false, false, null, RANDOM);
       }
       return random(count, chars.toCharArray());
   }

   /**
    * <p>Creates a random string whose length is the number of characters
    * specified.</p>
    *
    * <p>Characters will be chosen from the set of characters specified.</p>
    *
    * @param count  the length of random string to create
    * @param chars  the character array containing the set of characters to use,
    *  may be null
    * @return the random string
    * @throws IllegalArgumentException if <code>count</code> &lt; 0.
    */
   public static String random(int count, char[] chars) {
       if (chars == null) {
           return random(count, 0, 0, false, false, null, RANDOM);
       }
       return random(count, 0, chars.length, false, false, chars, RANDOM);
   }
   
}
